In most high energy neutral particle beam applications it is desirable to know the output power from the system as a function of both space and time. This is especially true for applications in outer space such as those contemplated for strategic defense against intercontinental ballistic missiles. For these outer space applications a device does not currently exist for measuring this output power. Thus, a need still exists for a monitoring device that is simple, easily built and maintained, easy to use and which measures both the total power in a particle beam and the spatial distribution of the particles within the beam.